Method of forming artificial teeth



- March 28, 1944 H. M. THORNTON METHOD OF FORMING ARTIFICIAL TEETH filed May 3, I941 3 Sheets-Sheet 1 HENRY M THORNTON ATTORNEY INVENTOR March 28, 1944.

H. M. THORNTON METHOD OF FORMING ARTIFICIAL TEETH Filed May 3, 1941 3 Sheets-Sheet 2 MIMI! will] NIH) m llh lll fn INVENTOR HENI? Y M. THOfi/V 701v ATTORNEY March 28, 1944. 1-1, M H N 2,345,305

. IE'IHOD DP FORMING ARTIFICIAL TEETH 4 mvzm'cm HE NR Y M 7/101? TON Patented Mar. 28, 1944 UNITED STATES, PATENT OFFICE,

2.24am Mn'rnon or roams ARTIFICIAL mm! Henry M. Thornton, York, 1%.. assignor to m Dentists Supply Company of New.York. New York, N. Y., a corporation of New York Application May 3, 1941, Serial No. 301,68!

; 3 Claims. (01. iii-55.1)

This invention relates to artificial teeth and methods 01' forming the same from plastic material.

Heretfore,it has been common practice to make artificial teeth from relatively high fusing porcelain materials, wherein the tooth is formed in a multi-part mould, and subsequently fired at a temperature, such as 2000* F. or higher, to vitrify the porcelain materials.

Plastic material, as contemplated herein, includes materials which will flow under high pressure and relatively low temperature compared to the fusing temperature of porcelain, and which will be substantially immediately hardened after introduction into the mould. Suitable plastic materials which may be employed are acrylics, styrenes, vinyls, phenolic resins and similar plastics. "Plastic materials as used herein is intended to cover not only thermo-plastic materials but suitable thermo-setting materials.

It is an object of my invention to provide improved methods of forming articles, such as artificial teeth, of plastic material.

Another object of my invention is to provide a method of forming artificial teeth which, in many instances, can be readily united with a denture base or plate without the use of a mechanical anchorage.

Another object of my invention is to provide a method 01 forming artificial teeth hardenable at relatively low temperatures, whereby numerous coloring materials impractical for high fusing porcelain teeth may be used.

Another object of ,my invention is to provide a method of forming artificial teeth of the above type which closely simulate natural teeth in appearance. 7

One method of practicing the invention is to provide a two-piece mould generally similar to moulds heretofore employed in forming porcelain teeth, but which is provided with a main gate in the mould and smaller gates extending from the main gate into individual tooth pockets. Plastic material of a desired viscosity is then forced under relatively high pressure through the gates into the mould and individual pockets.

Injection moulding machines are well known,

tooth in appearance. Under both reflected and transmitted light, many plastics have an optical similarity to the dentine and enamel of. natural, v

teeth/ Because of this fact the tooth surfaces, and particularly the labial surface, can be arranged to simulate natural teeth even thoush only one material is used; Additionally, slight irregularities may be provided at the labial surface of the tooth to create various eflects of shading.

To further simulate the appearance of natural teeth and create a more definite and natural blend between the incisal and gmgival portion'of the tooth. material of any suitable composition, organic or inorganic, such as glass fiber, glass cloth, metal, wood, plastic or porcelain pieces, or similar materials. of any color and ot any degree of opacity or translucency may be placed in the individual tooth pockets of the mould. The mould is then. closed and the plastic material injected. The deposited material will then become incorporated in the tooth and the deposited material can be initially shaped to give the tooth an appearance of being formed of body and enamel materials blended. in a natural manner. It is apparent that the shape and substance of this incorporated material is unlimited, and it may be shaped to form stripes, lobes, spots and the like, as well as to vary the translucence, opacity, or color in diiferentportions of the tooth. A second method of practicing the invention is to form the teeth in two stages. Either the body portion or the enamel may be formed as the first stage. If the enamel or veneer is first formed, a mould part conforming to the labial contour of the veneer is used in cooperation with a shader mould part conformingto the lingual contour of the veneer, so that when the mould parts are engaged a mould cavity corresponding in size and shape to the enamel or veneer is formed therebetween. Plastic material is then injected into the mould cavity under high pressure and the mould parts are subsequently separated so that the moulded veneer remains in the labial forming mould part. The body forming mould part then replaces the shader mould part on the injection machine and is engaged with. the labial forming mould part, thereby and any suitable machine may be employed for forcing the material into the mould. In this method only one material is employed, and by taking advantage of the variations in thickness of the tooth labially-lingually from the ingival third to the incisal third, and/or the surface contours of the tooth, variations in transluce'ncy and color eil'ect may be provided simulating a natural is I providing a cavity between the lingual portion of the veneer and the body-forming mould part, which will conform to the size andshape of the. body portion of. the tooth. Body-forming plastic I material is then injected into said cavity under high pressure, and after separating'the mould" parts, themoulded tooth is removed. Thus, by the use of suitable plastic material both for the over the lingual side of the veneer themouldpartsofl 'igures'land'sengaged Y "ing'depressions therein for veneer and for the body portion, a color blending fying agents employed. Also, the enamel maybe formed of one plastic material and the body portion of a different plastic material which is compatible with the veneer as to bonding qualities. For example, in the first instance, both the veneer and body material may be formed of acrylics, and in the second instance, the veneer may be formed of an acrylic and the body of a tyr A third method which I may employ isto inject plastic material into a mould cavity conforming to the enamel or veneer, and also to inject plastic material into a separate mould cavity conforming to the body portion of the tooth. These two separately formed parts may then be securely'united by painting or spraying a solvent or cement, for the particular plastic material or materials used, portion, or the labial side of the body portion, or both, andv quickly pressing the parts together in proper position.

It is further contemplated that a solvent or cement may be applied at the completion of the first stage, in the two-stage method, to the exposed surface of the part which is first formed. Also, to insure perfect adhesion, supplemental heat may be applied to the first formed part just prior to the second injection in the two-stage method.

into a cylinder I2.

the mould parts of Figures 1 and 12 engaged, taken along the line i3|3 of Figure 12,

Figure 14 is a fragmentary sectional view showing the manner of providing a mechanical anchorage in a tooth,

Figure 15 is a rear elevational view of a finished tooth showing outlines on the tooth lingual surface to which the tooth may be ground to alter the shape thereof,

Figure 16 is afront elevational view of a fin ished tooth, and

Figure 17 is a section taken on the of Figure 16.

Referring now to the drawings, and particularly Figure 6, I have indicated an injection moulding machine generally at 10. Injection moulding machines are well known, and any suitable type may be used, and the mould parts may be disposed to engage either horizontally or vertically. In the present instance, the mould ing machine is illustrated largely diagrammatically and the mould parts are disposed to engage horizontally. A supply pipe Ii extends from a supply hopper (not shown) to discharge material A ram I3 operates within cylinder i2 and may be actuated hydraulically to exert relatively high pressure, such as 30,000 lbs. per square inch. Cylinder i2 communicates with a press head It having a generally conical opening it therein. A generally cylindrical nozzle II communicating with opening It extends outwardly from the face of press head M. Sccured to the press head in any suitable manner, or formed integrally therewith as shown, is a generally box-shaped mould housing I8. A mould part I9 is mounted within and detachably secured to housing I8 by bolts or the like.

A'clamping ram 2! is adapted to bemoved axline 11- .ially by any suitable means, such as hydraulic The drawings illustrate embodiments of the invention and the views therein are as follows:

.Figure1is aplanviewof amouldparthaving labial tooth forming depressions therein.

Figure 2 is a plan view of a mould port adapted to cooperate with the mould part of Figure 1 having lingual tooth forming depressions therein, 7 Figure 3 is a fragmentary sectional view with the mould parts of Figures 1 and 2 engaged taken along the line 3-4 of Figure 2,

Figure 4 is a fragmentary sectional view with themouldpartsofriguresiandzengagedtaken along the line 4-4 of Figur 2. v

- Figure5isaplanviewofamouldedunitformed by employing the mould parts illustrated in Figures 1 and 2.

, Figure6isa :1 ticviewofaniniection moulding machine which I may employ.

Figures 7 ands are plan views of cooperating mould parts adaptedto form the body portions ofthetceth,

Figure9is'aplanviewohamouldedunit formed by the mould parts of Figures 7 and 8,

Figure 10is aplanviewofthemouldedimit. ofFigursil afterveneerh'asbeenmouldedtothe body portions of the teeth.

' Figure 11 is a fragmentary section showing ofrlgure 'lands, viewpfammildparthavformlnstheiingual' along the lines i-li l'lgureslzisaplan surfaces of the teeth,

, each of the depressions Ii is provided with a ri uresisaammenmmtioominns pressure, and is provided with a cooperating mould housing 22. Detachably mounted within housing 22 is a, second mould part 23 adapted to be maintained in pressure engagement with mould part l9 by clamping ram H.

The mould parts are illustrated in detail in Figures 1 to 4, inclusive. Mould part I! has a surface 24 substantially flush with the peripheral portions of housing i8, and generally centrally of the mould part is a slightly elevated surface- 26 having depressions 21 formed therein. Depressions 21 are adapted to form the labial portion of a tooth, and may be provided with slight irregularities, such as elevations, to form corresponding irregularities in the labial surface of the finished tooth.

Mould part 23 is provided with a surface 28 substantially flush with the peripheral portions of housing 22. A slightly concave surface 2! is provided generally centrally of mould part 23 within which are formeddepressions 3| adapted to form the lingual portions of the teeth. A generally U-shape main gate 32 is provided in mould part 28, and smaller gates 33 afford communication between the main gate and the depressions 3|. Pins 25 adapted to be received in holes Ii maybe provided for maintaining the mold parts in proper alignment in engaged position.

As best indicated in Figure 3, nozzle ll extends through mould part it to communicate with taken 10 main gate 32. Spaced holes it are provided in main gate 32 for receiving knock-out pins 35, and

hole 86 for receiving knock-out pins 31. Mould part 23 has a hole 38 therethrough adapted to receive a knock-out pin 30. The upper portion of hole 88, asindlcated at 4|, is of enlarged uh one plastic material, and in a single stage will now be described: A desired quantity of plastic material, preferably in granular or powdered form, will be dischargedinto cylinder i2 from simply conduit ll after retracting ram II to uncover conduit ii. The material in the forward portion of cylinder I2 is preferably heated, asby resistance coils 42, so that this material is in a plastic and/or semiplastic state. The knock-out pins are arranged as illustrated in Figures 3 and 4, and, are carried forwardly with clamping ram 2i as it advances surface of the moulded tooth as. a Illlde to the dentist in shaping the tooth to whichever outto engage the mould parts I! and 23, whereby the surfaces 24 and 28 of mould part ll will be inmating contact with surfaces 28 and 2! of mould part 23. Of course, sumcient pressure will be applied to clamping ram 2| to maintain the mould parts in sealing engagement during the moulding operation. Cylinder ram it will then be moved forwardly under relatively high pressure to discharge a desired amount of material through nozzle II, gates 32 and 33, into" the tooth cavities it formed between the engaged mould parts. Due to the high pressure under which the material is injected, it reaches all of the tooth cavities substantially instantaneously. Thus, a material which hardens quickly, and at a relatively low temperature can be used. The moulded teeth are indicated at M, and after the moulding operation, which requires only a short interval, the mould parts are separated, by withdrawing clamping ram 2|, and the material which has been forced into undercut'portion ll of mould part "insures that the moulded uni-t 46 will remain in mould part 23.

When ram 2| is reversed to disengage mould line he may desire, for example. square, tapering or ovoid. Thus, a single tooth will provide a choice of two or more contours and the tooth can be shaped to a desired contour by grinding to the outline. This eflects a considerable reduction in the number of tooth sizes and forms necessary.

Figure 15 illustrates a rear elevational view ofa finished tooth having the gingival two-thirds thereof of generally square outline, as indicated 7 at 40. A tapering outline a, indicated in dotted lines, may be provided on the lingual surface in any suitab1e'.manner as by providing corresponding ridges or grooves in depressions ll of back mould part 23. If ridges 'are provided, the outline loa will appear on the finished tooth in the form of depressed lines, and if grooves are provided in depressions oi, the outline will appear on the finished tooth in the form of ribbed lines. Of course, these outlines may be marked on the tooth by a suitable instrument subsequent to the moulding operation, if desired. I have indicated at 45 an outline of generally ovoid form.

To further improve on shading and naturalness, and create a more definite and'naturalblend between the incisal and gingival portions of the teeth, material of any suitable composition, organic or inorganic, may be placed in the individual tooth cavities or pockets of the mould prior to engaging the mould parts. After the plastic material is injected this material will be parts I! and 23 the plastic material extending from nozzle ll to. main gate 32 is extracted from the nozzle by undercut 4| in mould part 23. The knock-out pins may be attached to a plate I1, and this plate may be withdrawn a predetermined .distance with clamping ram 2i, and then held in a fixed position while the clamping ram continues to retreat, and thus, projecting the knock-out pins forwardly into main gate 32, depressions 3i, and hole 38 to force the moulded unit from mould part 23. The knock-out pins will subsequently be withdrawn to the position shown in Figures 3 and 4, and the cycle of operations will be repeated.

I have found that even though only one plastic material is employed in the above described process, that the optical similarity of plastics in artl-.

flclal teeth to natural teeth under both reflected and transmitted light, and the tapering of the teeth labially-llngually from the gingivalthlrd to theincisal edge will create a natural eifect of shading and translucency. Also, irregularities may be provided on the labial surface of the ease with which teeth of this type may be shaped, I y provide one or more outlines e; th 1mm incorporated in the'moulded tooth, and since the plastic material hardens at a relatively low temperature, as compared to the fusing temperature of porcelain teeth, a wide variety of materials may be employed which would be impractical in porcelain teeth. For example, glass fiber, glass cloth, metal, wood, plastic or porcelain pieces',or many other compositions of various colors and opacities may be used. This material may have any desired degree of opacity and can be so shaped initially to give the finished tooth the appearance of being made of body and enamel materials blended in a natural manner. The material may be shaped to form stripes, lobes, spots and the like as well as to vary the translucence, opacity or color of difl'erent portions of the tooth.

The teeth may be removed from moulded unit 46 by a trimming operation and the individual teeth can then be subjected to polishing and the like if desired.

Two-Stage Process Informing the teeth in two stages, ploy mould parts I! and 52 illustrated I may em in Figures 7 and 8 respectively. These mould parts are simfrom extending to the incisal portion of the teeth,

and this is efl'ectcd by providing an elevated lip It at the incisal portion of depression II. The

lingual surfaceforming depressions 84 in mould part 52 are provided with a mating recess or shelf II for receiving lip 5i. Thus, when the mould parts, are engaged, as illustrated in Figure 11, the resulting cavity conforms to the body portion of the tooth. As illustrated in Figure '1,

Since it is desired to portion will extend incisally pression in mould part into the -color, as illustrated in the depressions 53 adapted to form the labial surface or the body portion ll may be provided with. grooves 59 which will result in an elevated stripe 60 on the moulded body portion, and this groove may beextended into lip It. as indicated at 6|, so that the resulting stripe on the body beyond the body and in the finished tooth will the relatively translucent enamel into the enamel incisal portion. Also, lip 56 may be provided with arcuate concavities 62 so that the moulded body P t on will terminate incisally in the form of rounded projections, which will appear through the enamel of the finished tooth in the form of lobes. The depth of the concavities which form these individual lobes may be varied in relation toeach other so that efiects caused by over or under development of dentine segments in natural teeth may be reproducedin artificial teeth. Mould parts and 52 will be mounted in housings II and 22 and the mating parts will be engaged and the body material in- ,Iected as described in the single stage process. The moulded unit indicated at 63 in Figure 9 is then removed from mould part 52 and the unit portion proper, appear through as a stripe extending is cut to remove dotted portion 84 and provide individual bars 65 each-having body portions 55 attached thereto. portions are then disposed in channels 66 and depressions 61 provided in a mould part 80. Each depression 61 is a replica of a corresponding de- 52 except that the depression 61 is slightly deeper at the incisal area, as indicated at 10 in Figure 13, to allow enamel to fiow under the incisal termination of the body portion and thereby insure more strength in the tooth as well as a closer simulation to natural teeth, and the depression 81 extends beyond the body portion incisally so that when mould part is of Figure l is engaged with mould part '8, a cavity is formed between the labial surface "a of the body portion and the depression 21 for receiving the enamel or veneer. If a single injection machine is used, a desired number of moulded units 63 may first be made, and then the mould parts El and 52 are replaced by mould parts 68 and IS, the bars 65 and. attached body portions are placed in mould part 68, as previously described, and the brought into e'ngagement' Enamel material is then injected into the veneer-forming cavities 00, the material fiowing from nozzle I'I through a centrally disposed main gate Ii, and smaller gates 12 to the individual veneer cavities 6!.

The moulded unit indicated at I3 is then removed from mould part 68 and the individual teeth severed therefrom, as previously described; It will be noted by reference to Figures 11 and 13 that theclevated stripe surface of the body portion 55 extends into the veneer-forming cavity 69 and provides a thinnedout area in the veneer so that the through th translucent veneer in contrasting Figure 10. In the same manner the lobe formations on the body portion 55 appear through the veneer in contrasting color to simulate markings frequently found in natural teeth.

' Figures 16 and 1'7 illustrate a finished tooth wherein the veneer overlies the mesialand distal sides of the body portion, as indicated at N, and the veneer may be extended any desired distance gingival area of the tooth. Also, the

surfaces of the mould Bars 5 and the attached body mould parts are- 80 formed on the labial v asiasos they stripe appears this projection veneer overlies the lingual incisal surface of the Is 'incisal portion of portion and styrene material .ing a solvent or cement for body portion, as indicated at II, and thus an enamel veneer jacket is provided forming the labial, mesiaL- distal and lingual surfaces of the body portion.

It iii-understood that the bodyportion S! will be shaped by the mould parts Ii and ii to provide space along the mesial and distal sides of the body portion for receiving the veneer material when it is desired to have the veneer extend along the mesial and distal sides of the tooth, as illustrated in Figure 18. The veneer-forming cavity Ql, in this instance, will include the space intermediate the body portion and the mesial and distal sides of depressions 21 provided in face forming mould part is. I

The enamel material is translucent relative to the material of the bodyportion l5, and the body material may be or the same composition as the enamel material with a coloring agent or opacifier added thereto. Also, a plastic material of one class may be used for the bodyportlon and a plastic material of another class used for the enamel it the materials are compatible as to bonding or adhesive qualities! For example, acrylic'material might be employed for the body for the enamel. Prior to injecting the enamel material a solvent or cement may be applied to the surface a of the tooth body portion, or heat may be applied to the exposed surface a of the body portion just prior to injecting the enamel material.

01 course, organic or inorganic coloring material as described stage process may be I portion, enamel portion, or both, to further simuiate the appearance of natural teeth.

Although in the two-stage process the body portion was first formed, it is understood that the enamel or veneer may be first formed and the body portion injected as the second-stage. In first forming the enamel a mould par-t similar to mould part is of Figure 1 would be used in cooperation,with a mould part having convex surfaces conforming to the contour of the lingual surface of the enamel, or individual auxiL iary dies of the same shape may be mounted in depressions ii of mould part 2| of Figure 2. The use of these dies would reduce the number of mould parts required and could be secured by a pin adapted to seat within holes 3' of depressions I i Third method A third method of forming artificial teeth of plastic material having a translucent enamel veneer and a relatively opaque body portion is to separately mould the enamel and the body portion. of course, this would require the use of four moulds. These two separately formed parts will, then be securely united by paintin or spraymaterial used over the lingual side of the enamel portion or the labial side of the body portion or both and quickly pressing the parts together in proper position. If one class of plastic material is used for the enamel and another class for the body portion a bonding agent compatible with both materials would be used.

It will be noted by reference to Figure 1'1 that a projection '2 formed 0; the same material as the body portion lingual surface thereof, and that the extent of may be controlled as desired through the positioruns or knock-out pins 31 our 7 the tooth'and overlying the in connection with the oneincorporated in the body described I as body portion ll the particular plastic 1 II of the tooth extends from the ems v I 5 ing the moulding oi the body portion at. These projections serve as anchoring means for attachment of the teeth to a denture base or the like.

In Figure 14,- I have indicated a conventional mechanical anchorage I. which may comprise a I metallic pin having an enlarged head adapted to beembedded in the body portion during the moulding operation. The anchorage 18 may be disposed in the body forming depressions and supported on knock-out pins 31 so that body mate'rial may flow under the head portion and se- I curely embed it in the body portion.

Although for purposes of illustration, 1 have shown mould parts adapted to concurrently mould twelve anterior teeth, or teeth portions,

it is understood that any desired number of anterior or posterior tooth cavities or pockets may be provided in the mould parts or that an in- 1 dividual nozzle mayinject tooth" material conof color material may be used, teeth closely simulating natural teeth in appearance may be provided.

Although I have shown and described preierred forms or my invention, I contemplate that numerous and extensive modifications may be made without departing from the spirit of my invention and the scope of the appended claims.

The invention is hereby claimed as follows:

moulded tooth will beretained in the mould part provided with the port, and electing the moulded tooth by pressure exerted at the port, whereby an anchoring projection isrormed on the lingual surface of the tooth by the material projected into the port during the moulding operation.

2. The method of forming artificial teeth from plastic resins by injection moulding which cornprises providing separable metal mould parts having moulding surfaces adapted to form a tooth cavitytherebetween when engaged, disposing solid pre-iormed coloring material in. one or said moulding surfaces adapted to retain its form at the hardening temperature of the plastic 1 resin material, engaging said mould parts under high pressure, and then injecting the plastic resin material into the mould cavity under high Pressure while heated to a flowable condition to concurrently mould and finish harden the plastic resin material and incorporate the coloring material. therein.

3. lhe method of forming artificial teeth of the type comprising a relatively translucent veneer portion and a relatively opaque body por- 25 tion from plastic resins 'by injection moulding, said method comprising the steps of providing a three-part metal mould, with two of said parts being adapted to form one portion of the tooth, engaging the two said mould parts under-high pressure, injecting plastic resin material underhigh' pressure and in flowable condition into said mould parts to concurrently mould and harden Tone portion of the tooth, separating the mould parts while retaining the moulded portion in one 1. The Of forming fl 'fiflii ll rm 35 mould part engaging the mould part under plastic resins by injection moulding which comprises providing metal separable mould parts adapted to form a tooth cavity therebetween when engaged, the mould part adapted to form the lingual surface of the tooth having a port extending to said lingual mouldim surface en- .gaging said mould parts under high Pm. closing a portion of said port, injecting plastic resin material into the'mould cavity under high portion, and theniniecting plastic resin material of dill'erent composition from the first injected material under high pressure and in flowable conditionto finish harden said portion of the tooth and concurrently completely mould the pressure while heated to a flowable condition to tooth and unite both tooth portions.

concurrently mould and finish hardm said material, separating the mould parts, whereby the HENRY ll. THORNTON. 

